Chloroaniline antifoggants



Patented Sept. 11, 1945 Eastman Kodak Company, Rochester, N. 1., a corporation of New Jersey lilo Drawing.

This invention relates to tog inhibitors for photographic emulsions and to photographic emulsions containing them.

It is known that photographic emulsions, particularly ultra-sensitive emulsions, exhibit a tendency to form a deposit of silver in the unexposed emulsion. This deposit extends more or less uniformly over the entire emulsion and is known as fog. Photographic tog is or two types, local and general. Local iog ,is formed by exposure oi the film or plate at undesired points, as by a light leak in the camera, or by local action of chemicals. General log or, as it is sometimes known, chemical tog, is formed in a, number of ways. It may be caused by the conditions under which the fllm or plate is stored, such as conditions at high temperature or unusually long tiine oi storage. The nature oi the emulsion may also produce chemical fog, as well as the conditions of development 01 the emulsion, as by development for protracted periods of time or at temperatures above normal. Highly sensitive emulsions are more likeLv to log than those of lower sensitivity. I am concerned primarily. with general or chemical fog. i

It is an object of the present invention to provide anti-fogging or fog inhibiting agents for ultra-sensitive photographic emulsions and thereby to preserve the emulsions against deterioration resulting in fog. A iurther object is to provide antifogging agents which do not markedly lower the sensitivity of the emulsion. Other objects will appear from the following descrip tion of my invention.

msgbjects are accomplished by developing 35 an exp d silver halide emulsion in the presence of a chloroaniline, preferably by incorporating the chloroaniline in the emulsion.

These compounds may be incorporated in an emulsion, particularly a fast negative emulsion, to which may be added optical sensitizing dyes. The emulsion may be one which is intended to be used directly after emulsiflcation or one which is subjected to ripening.

45 Chloroanilines which I have found suitable for inhibiting fog in photographic emulsions include o-chloroaniline, m-chloroaniline, 2,5-dichloroaniline and 2,4,6-trichloroaniline, which 'is a pchioroaniline.

Application January 13, 1944, Serial No. 518,122

11 Claims. (Cl. 95-8) The antiioggant-properties .oi the chloroanilines are tested as follows:

Silver iodobromide was-precipitated in 0.8% gelatin solution. After precipitation was complete this entire volume of emulsion was cooled and divided into portions weighing 1643 grams each. To each portion was added enough gelatin to increase the gelatin concentration to approximately 6.6%. Each portion was then heated to the required digestion temperature, that is, about 60 C., and as soon as this temperature was reached a certain amount of the compound to be tested, e. g., 25 grams of o-chloroaniline, dissolved Sodium suliite -(desiccated) do 96 Hydroquinone dn 8.8 Sodium carbonate (desiccated) do 48 Potassium bromide ;do 5 6.0 Water t: 1

in 300 cc. of methyl alcohol, was added. Digestion was then continued for 30 minutes at the specified temperature and the emulsion was then chilled and stored in preparation for shredding and washing. One or these portions received no additions other than the required gelatin and it served as the control for all the portions originating from the sameprecipitation of silver halide.

Alter washing, each emulsion was heated to the optimum point for maximum speed and aiter coating, similar tests on a second set 01 plates incubated at 120 F., dry heat, for 14 days and a third set of tests made on a third set of plates after having been kept under tropical con-- ditions for. 14 days. (The "tropical conditions are simulated by varying the temperature and humidity through a cycle to reproduce day and night conditions in tropical climates.) Plates for each of these .tests were developed for 3 minutes at 65 F. in Kodak D-l9 developer which had the following-composition:

Monomethyl-p-aminophenol suliate-grams 2.2

The results of these tests are tabulated below,

in each case the amount of chloroaniiine bein! 12.5 grams per 1000 cc. of unsensitized wet emul 1. A gelatino-silver halide emulsion containing a tog-inhibiting amountoi a chloroaniline containing only one amino group and free of hy- 51011- droxyl groups.

Tro ical condition l4-day 120 F. dry ag 1 my incubation incubation 03 log tests log tests Name of compound Emulsion Emulsion Emulsion Emulsion Emulsion Emulsion with without with without with without comcomcomcomcomcompound pound pound pound pound pound o-Chloroaniline 0. 05 0.07 0. 06 0. 10 0.15 0. 33 m-Chloroaniliue .05 .07 .05 .06 22 .38 2, odlchloroaniline 05 .07 06 10 33 2, 4, fi-trichloroaniline 05 04 06 11 80 90 The amount of fog was determined by reading the density on the unexposed area or the test after exposure and development of the emulsion, in the usual manner.

The amount of the fog inhibiting agent used in the emulsion will depend upon the composition of the agent and upon the type of emulsion. In genera], the amount'oi iog inhibiting agent used will vary from 1 gram to 15 grams per 1000 cc. of wet emulsion. It will be understood that more or less than this amount may be used. Generally, however, if a greater amount is used in the emulsion, either no increased iog inhibiting effect is obtained or there is a decrease inthe sensitivity of the emulsion. These compounds may be incorporated by mixing them with any suitable solvent which is relatively inert with respect to the emulsion such as water, methyl alcohol, ethyl alcohol, acetone and others.

The log. inhibiting agents which I have described may be used in various kinds of photographic emulsions. In addition to being useful in ordinary non-sensitized emulsions, they may be used in orthochromatic, panchromatic and X-ray emulsions. Various silver salts may be used as the sensitive salt such as silver bromide, silver chloride, silver bromoiodide, and silverchlorolayer in the photographic element containing the sensitive emulsion layer.

It is to be understood that I contemplate as included within my invention all modifications and equivalents falling within the scope of the appended claims.

I claim:

- a fog-inhibiting amount of an o-chloroaniline containing only one amino group and free of hydroxyl groups.-

4. A gelatino-silver halide emulsion containing a fog-inhibiting amount of a m-chloroaniline containing only one amino group and free of hydroxyl groups.

5. A gelatino-silver halide emulsion containing a fog-inhibiting amount of a p-chloroaniline con taining only one amino group and free of hydroxyl groups.

6. A gelatino-silver halide emulsion containing a tog-inhibiting amount of o-chloroaniline.

'7. A gelatino-silver halide emulsion containing a fog-inhibiting amount of m-chloroaniline.

8. A, gelatino-silver halide emulsion containing a fog-inhibiting amount of p-chloroanlline.

' 9. A gelatino-silver halide emulsion containing approximately 12.5 grams per-liter of a chloroaniline containing only one amino group and tree of hydroxyl groups.

10. The method of reducing the amount 0! log produced upon development of a silver halide emulsion, which comprises developing said emulsionin the presence of a fog-inhibiting amount of a chloroaniline containing only one amino group and free of hydroxyl groups.

11. The method of reducing the amount of fog produced upon development oi a silver halide emulsion which comprises developing said emulsion in the presence of a fog-inhibiting amount or a monochloro aniline containing only one amino group and free of hydroxyl groups.

GEORGE E. FALLESEN. 

